Dresden 2006 – scientific programme

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MA: Magnetismus

MA 33: Spin-Dynamics, Magnetization Reversal III

MA 33.11: Talk

Thursday, March 30, 2006, 17:45–18:00, HSZ 403

Femtosecond Spin-Dependent electron Dynamics in Co thin films — •Mirko Cinchetti, Marina Sánchez Albaneda, Oleksiy Andreyev, Jan-Peter Wüstenberg, Michael Bauer, and Martin Aeschlimann — University of Kaiserslautern, Physics Department, Erwin Schroedinger-Str. 46, 67663 Kaiserslautern, Germany

Using the energy-, spin- and time-resolved two-photon photoemission technique, we have been able to follow the ultrafast spin-dependent electron dynamics in an epitaxially grown Co thin film. We observe that the time evolution of the spin polarization of unoccupied intermediate states (lying between the Fermi and the vacuum level) shows remarkable differences in dependence of the energy of the unoccupied state itself. In particular, for high intermediate states energies we find an increase of the polarization within the first 50 fs, which is due to the lifetime difference between spin-up and spin-down electrons. On the other hand, at low energies we find a modification of this behavior up to 700 fs. This is mainly due to secondary electrons which are scattered into the intermediate state, leading to refilling of the state itself. Within these 700 fs we can distinguish between a spin-selective region (with almost no spin-flips) and a spin-flip region, where a dramatic drop in the polarization is observed. The reasons for this behavior are discussed.